If you have caller ID and sales calls irritate you, why do you insist on answering calls from numbers you don't know? Telemarketers flag people who willy-nilly answer their phones silly.

There is a Federal "do not call list" that you can join for free. If you tell a caller "put me on your do not call list", they are required by law to stop calling you.

However, many callers are scams and ignore the law. The local police won't help you. The phone company will just tell you to complain to the FCC, which only busts the companies with the most complaints.

That leaves caller ID. Depending on who you get your phone service from, it may or may not be free or cheap. Some phones have audible caller ID, so you don't have to look at the phone to see who is calling.

Actually, does the caller ID give you a number? if not, after you sign up for the Do Not Call list, you could add anonymous caller blocking so people have to reveal their numbers to call you. If they persist, then you write down the number or take a photo of the time and number, and tell them, "Put me on your Do Not Call list. I am logging this call, and if you call me 3 times [or whatever it is], I will seek damages in small claims court." You can get like $1500 if they call you again 3 times. It usually doesn't come to that, but reminding them you know your rights (look them up of course to be exact) usually helps.

Also, log the information and file a complaint with the FCC. That also helps. They can't go after spammers unless people complain. A small number of people account for most of the problem, so it really is worth your logging the calls and complaining.

Just write down an unfamiliar phone number and Google it. Most times it turns out to be a scam, easily corroborated by posts on 800 Notes or some other website that will come right up in the search.
It is clear that many of us on the do not call list (and who have renewed it) are still getting nuisance/scam calls frequently and the system is ineffective.
If you are concerned about missing a legit phone call by screening (not picking up the phone right away), just listen for a legit caller starting to leave a message, and then pick up. The majority of scammers/spoofers do not leave any message. I now have quite a list of "bad" phone numbers, but they keep switching numbers and it's virtually endless. I am about at the point of discontinuing our landline as this is annoying. Asking a scammer to take you off their list, or threatening them with reporting them for calling, or "pressing X to get taken off the list" all do not work.
two sales calls a day isn't bad, if you check out reports on the net!
What is sad is that politicians refuse to take action against these vile phone scammers, and sometimes people are even victims if they are unaware and easily taken advantage of.

Yes, we have Caller ID, and I have blocked calls and reported the phone numbers. Here is the link to report to the FTC: Web Link
As someone mentioned, reporting will stop them one by one.

To the person who posted to just not answer the call, my issue is that a phone ringing is still a disturbance. I suppose I could disconnect the ringer and just allow the machine to pick-up each time. But why should I have to? Why is harassment legal?

I am on the do not call list, the scammers don't honor it and they spoof their phone numbers which is easy to do if you are using VOIP.

You could try using a device like this.

Web Link

We are able to block most of them that way.

[Post removed.]

I am already on the Do Not Call List.

Thanks for the link to the device, "does not work". I will check into it.

It's supposedly illegal for sales call cell phones, according to the FTC.

Nomorobo, Web Link can help significantly. I love it.

Here's a description about how it works:
Web Link

Here's a CNET article about the subject that includes a nomorobo how-to guide:

Web Link

Thanks so much, Alison!

Thanks, Alison. Unfortunately, 'nomorobo' does not work for ATT customers. So I guess I'll keep guessing whether the unfamiliar 800-number is from a spammer or my Sears delivery call.